Telephone exchange system



y 1933- H. HENRY El AL A 1,915,761

TELEPHONE EXCHANGE SYSTEM Filed Aug. 23, 1952 9 Sheets-Sheet 1 MA RG/NAL l l I INVENTORS 9&M

' ATTORNEY July 4, 1933. HENRY r AL 1,916,761

TELEPHONE EXCHANGE SYSTEM Filed Aug. 23, 1932 9 Sheets-Sheet 2 HE NR) HERSEY A T TORNEV H. INVENTORS RE July 4, 1933. I. H. HENRY ET AL TELEPHONE EXCHANGE SYSTEM Filed Aug. 23, 1932 9 Sheets-Sheet 3 mew mew mum 8% N\ mm UR QM UR umumt SID )l lulul Dll l-il ul F llini- \JIeIIIII Pl llll ollllln QlllllD 'olll al-nnlnilllln ill QRALE h July 4, 1933. HENRY AL 1,916,761

TELEPHONE EXCHANGE SYSTEM H. HENRY /NVEN7'OR$ RE HERSE},

ATTORNEY July 4, 1933. HENRY ET AL 1,916,761

TELEPHONE EXCHANGE SYSTEM Filed Aug. 23, 1932 9 Sheets-Sheet 5 MARG/NAL ATTORNEY July 4, 1933- I. H. HENRY ET AL TELEPHONE EXCHANGE SYSTEM 9 Sheets-Sheet 6 HHENRV RE. HERSE) ATTQRNZY INVENTORS Qmd y 9 l. H. HENRY ET AL 1,916,751

TELEPHONE EXCHANGE SYSTEM Fi led Aug. 23, 1952 9 Sheets-Sheet 7 POLAR/ZED MARG/NAL IHI' FIG. 7

July 4, 1933. I. H. HENRY ET AL 1,916,761-

TELEPHONE EXCHANGE SYSTEM Filed Aug. 2:5, 1932 9 Sheets-Sheet 8 Ali-HENRY INVENTORS R E HERSE,

A 7' TORNEV FIG. 8

July 4, 1933. l. H. HENRY ET AL 1,916,761

TELEPHONE EXCHANGE SYSTEM Fil ed Aug. 23, 1932 9 Sheets-Sheet 9 Mm 8". @am

ATTORNEY FIG. 9

Patented July 4, 1933 UNITED STATES- PATENT OFFICE ISRAEL I-I. HENRY, OF EAST ORANGE, AND RALPH E. OF MADISON, NEW

JERSEY, ASSIGNORS TO BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW' YORK, N. Y., A CORPORATION or NEW YORK TELEPHONE EXOHANGE' SYSTEM.

Application filed August 23, I932; Serial No. 630,010.-

This invention relates to telephone exchange systems and more particularly to cirlish more connections-within a stated period it'- provision is made to enable the operator to write up the designations of desired connections upona keyset at her position. Such an arrangement has heretofore been disclosed for enabling toll operators to complete con nections over panel dial switchingequipinent in the Patent No. 1,780,906 granted November 11, 1930, to WV. W'. Carpenter and R. E. Hersey. I

In accordance with the present invention, provision is made whereby an operator may set step-by-step switches to complete local or toll connections under the control of a set of ten digit keys at her position; This is accomplished through the provision of a sender which becomes associated with the outgoingtrunk circuit taken for use by the operator to complete the desired connection, which sender is arranged to record the digits of the line designation keyed by the oprator and to transmit directive impulses to stepby-step switches accessibleov'er the outgoing end of the trunk circuit.

In step-by-step exchange systems the switch trains for completing connections may comprise a variable number of selector switches dependent upon the character of the call to be established. For the purpose of discriminating between classes of calls the trunks outgoing from the operators position are divided into groups, four for example, each group'being individual to a particular class of call. All trunks have access through a group of link circuits to a group The obof senders. Any trunk taken for use by the operator becomes automatically connected to an idie sender immediately after the operator plugs a cord circuit of her position into the trunk jack. may knowwhat class of call it is to control and therefore how many series of impulses itshould transmit to selector switches provision is made in the trunk circuit for set;

ting up in the sender a class record cor-re sponding to the group or class to which the particular trunk belongs. F or this purpose each trunk, dependingupon" the group to which it belongs, establishes class registra-. tion circuits from the trunk to the sender as soon as the sender becomes connected to the trunk, over four control conductors, two of which are later used for transmitting digit registration control impulses from the operators keyset and two of which later form the impulsing loop from the sender to the selectors to be set thereby.

Four class records are thereby set up in the sender corresponding to the four groups of outgoing trunks. .Tnese classes'may be fixed, where all connections to be established by the sender will require the transmission of the same number of di 'it series, or may be variable, where some connections made over the group of trunks may require a dif ferent number of digit series than other connections over the same group. The grouping of the trunks and the corresponding class record established'in the sender may also indicate whether or not immediate ringing is to be applied from the sender. This feature of settlng up a class registration in the sender has beenmade'the subject matter of an application of I. H. Henry, Serial No. 630,-

009, filed herewith.

On calls recorded in the'sender asvariable class calls a start indication is keyed by the operator which indicates to the sender when the'operator has'completed keying the entire designation of a call. Foralliixed class calls the sender begins to transmit impulses in accordance with any registered digit as's oon as the digit is registered. For variable class calls the sender begin to transmit impulses in accordance with any registered digit In order that the sender" as soon as the digit is registered or, it desired, may delay the sending of impulses for any registered digit or digits until a succeeding digit has been registered or until the operator has keyed the start indication.

For controlling the transmission of impulses from the sender to selector switches, two polarized relays are provided, the timing of whose operation is controlled through the charging and discharging of a condenser whereby timed impulses of a character which insures accurate setting of the selectors is attained. digit series transmitted is controlled by a group of seven pairs of counting relays which are operated in succession by the impulsing,. relays, the number of pairs of relays operated during the transmission of any digit being under the control of the register upon which the operator has registered that particular digit. The counting relays are also employed in conjunction with the impulsing relays for measuring off time intervals between successive digit series to allow time for selectors to hunt for idle trunks and are also employed for measuing oli' a time interval for the application of ringing current from the sender on such class calls as require immediate ringing from the sender. The time interval measured between successive digits for such variable class calls may be varied by changing the number of pairs of counting relays which will be operated in accordance with the class of call registration recorded in the sender.

For a more complete understanding of this invention, reference may be had to the fol lowing detailed description taken in connection with the attached. drawings in which:

Fig. 1 shows an operators cord circuit for extending connections to trunks extending to dial switching offices and a portion of the equipment at the operators position;

Fig. 2 shows the operators keyset and telephone set circuits;

Fig. 3 shows a trunk circuit of one group or class terminating in a jack accessible to the operators cord circuit of Fig. 1, and in a first selector switch and the diagrammatic representation of other selector switches and a called subscribers line;

Figs. 3B, 3C and 3-D show modified strapping necessary when the trunk circuit belongs to other groups or classes;

Figs. 4 and 5 taken together show a link circuit for associating a sender such as is disclosed in Figs. 6 to 9, inclusive, with the trunk circuit of Fig. 3. In Fig. 1 the trunk finder and in Fig. 5 the sender finder of the link are disclosed;

Figs. '6 to 9, inclusive, show a sender circuit, Figs. 6 and 7 disclosing control relay equipment of the sender, Fig. 8 disclosing the impulse counting relays and relays of three of the sender registers, and 9 show-' The number of impulses of any ing relays of the remaining registers or" the sender; and

Fig. 10 is a diagram showing the manner in which the several figures of the drawings should be assembled to disclose the complete embodiment of the invention.

The trunk finder L50 shown in Fig. 1 may be of the well known Strowger type having both rotary and vertical stepping movements, but being used as a hunting switch it is also equipped with a vertical group commutator and commutator brush. In addition, it 1s equipped with additional brushes to afford additional points of access to control conductors err-tending to trunk circuits.

The sender finder .550 of Fig. is of the well known step-by-step rotary type having no definite normal position and always remaining standing when idle on the terminals of the sender last used in extending a connection.

The selector switches disclosed diagrammatically in Fig. 3 may be of the well known Strowger type responsive to directive impulses transmitted thereto from the sender, but are preferably of the type usually employed for establishing toll connections.

Completion of a call from an intercepting trunk It will be first assumed that a call is incoming to the operators position of Fig. 1 over the trunk jack 100 from an intercepting trunk from a connector multiple and that the operator answers the'call by inserting plug 101" n of her cord circuit shown in Fig. 1 into jack 100. Aclrcuit is established thereupon from ground over the sleeves of jack and plug 101 to battery through the winding of relay 102 and the winding of marginal relay'103 in series and to battery in parallel therewith through the non-inductive winding 104 of relay 103. At the same time the trunk lamp (not shown) is extinguished. Relay 102 operates but relay 103 does not operate over a high resistance ground connected to the sleeve of the trunk employed for intercepting service from connector multiples, and

establishes a circuit for the supervisory lamp 105 extending from battery over the inner contact of relay 102, resistance 106, back contact of relay107, back cpntact of relay 108, to ground through lamp 105, and in parallel therewith from battery over the inner contact of relay 102, resistance 106, back contact of relay 107, back contact of relay 108, inner lower back contact of relay 109, inner normal contacts and winding of relay to ground at the lower right normal contact of key 111. Relay 110 looks ina circuit from battery at the inner contact of relay 102, inner upper alternate contacts and winding of relay 110 to ground at key 111. A circuit is now closed from battery through v When the 0 one winding" of the back; bridge relay of the connector (not shown) which has extended the connection to trunkjack 100, over theback contact of relay109, upper back contact of relay 137, resistance 138 to battery and from ground throught-he other winding of the back bridge relayof theconnector over the rings of jacklOO and plug 101, lower normal contact of key 114, lower left windinglof repeating coil 113, inner lower back contact of relay 103, intermediate lower back contact of relay 109, lower back contact of relay 137 to battery through high resistance v intercepting trunk circuit from a selector 139. Relay 108 does not. operate in this, circuit and due to the high resistance 139 the back bridge relay of the connector does not operate.

operator throws her listening key 111 to the right or talking position relay 110 releases and a circuit is established from ground at the outer left back contact of relay 201, conductor 112, upper ri htcontact of key 111 to battery through the winding of relay 117 which operates and establishes a circuit from battery at the inner contact of relay- 102,

inner lower contact of relay 117, conductor 115, to ground through the winding of relay 202, Relay202 operates and connectsbattery over its outer contact, winding of relay 203, resistance 204, right back contactof relay 201, conductor 205, middle lower contact of relay 117, resistance 119, middle lower back contact of relay 109, inner.- lower back con-- tact ofrelay 103,.lower left winding of repeating coil 113, lower: normal contactof key .114, rings of plug. 101 and jack 100 to the trunk circuit. Ringing current or silent interval battery operates relay 209 for relay 203, which connect ground through lnter- ,rupter contacts 206, contact of relay 209 or relay 203, back contact of relay 207 to battery through the winding of relay 208. Re-

: lay 208 operatesand locks through the winding of-relay 207 outer contact of relay 208 to ground atthe inner contactof relay 202. lVith relay 208 operateddirect ground is connected through resistance204 to the'ring of the trunk over the path traced for tripping ringing current'and for holding relay. 203

operated. When the interrupter contacts 2065.

again open,-relay 207 operates in the locking circuit of relay 208 and both relays are then held operated to ground at the inner contact of relay 202. When the interrupter contacts again close with relay 207 operated, relay v201 operates in a circuit from battery through its winding, front contact of relay 207, 'frontv the operators telephone set 213 thus produccontact of relay 203-to ground at interrupter contacts206." Relay 201 lockover'its right front contact to ground'at the inner contact ofrelay202, opens the ringing: circuit from series with relay 102.

the-ringof the trunk through'resistance 204 and the windings of relays 203 and 209, closes an obvious circuit through the upper winding of relay'200 and removes direct ground from the operating circuit of relay 117 in the cord circuit. "Relay 117 is now held operated over the previously traced circuit to ground through resistance 210. Relay'117 multiple, not requiring the tripping of machine ringing, relay 201 would. be operated over conductor 118, inner upper contact of relay 117 to ground at the contact of relay 103 which in this case will be operated in Relay 201 upon operating will cause the operation of relay 200.

With relay 200 operated, a talking path established from the upper right winding of repeating coil 113, inner upper right contact of key- 111, conductor 120, upper contact of relay 200, right winding of repeating coil. 211, condenser 212, lower contact of relay 200, conductor 121, inner lower right contact of key 111, to the lower right winding of repeating coil 113; Assuming that the operators telephone set 213 is plugged up, the talking path just traced is inductively associated therewith through the left winding of repeating coil 211 and the operator is enabled to converse with the calling subscriber to ascertain information concerning the desired connection.

It will'be assumed that the desired connectlon is of a character which can be com pleted over a trunk such as is shownin Fig.

3, with the straps 301, 302, 303 and 304 connected as shown to join conductors 305 and 306, 307 and 308, 309 and 311, and 312 and 313, and with straps 325, 326 and 327 also connected. The operatorlirst' tests. for an idle trunk of the group by touchingthc tip of plug 122 to the sleeve of the ack'of a trunk of that group. If "the trunk is busy there will be battery potential on the sleeve and this potential will be transmitted over "the tip of plug 122, the upper normal contacts of relay 123, the upper back contact of relay 124,'the upper normal contact ofkey 125, conductor 126, condenser 214 to ground through the upper right'winding of repeating coil 215 which induces the busy potential through the left winding of coil 215 into ing a click in her receiver. Assuming that she tests the trunk circuit of Fig. 3 and finds that it is idle andreceivesno click, she inserts plug 122 into jack 314 thereby establishing a circuit extending from ground through the windings of relay 315, sleeves of jack 314 and plug 122, windings of relay at its upper back contact and at its inner upper and inner lower front contacts, connects the tip and ring contacts of plug 122 to the right windings of repeating coil 113. Relay 127 at its lower contact also establishes a circuit for lamp 130 extending over the upper back contact of relay 131. Preparatory to keying the digits necessary to complete the connection the operator now depresses the key 216 and with the talking key 111 operated to the right a circuit is established from ground at the lower back contact of relay 218, the right contact of key 216, conductor 217, the lower intermediate contacts of key 111, the upper winding of relay 123 to battery at the lower contact of relay 124. Relay 123 thereupon operates and locks in a circuit -from battery over the lower contact of relay 1.24, lower winding and inner front contact of relay 123, conductor 132, back contact of relay 219 and in parallel to ground through resistance 220 and the winding of relay 218. Relay 218 operates in this circuit opening the initial operating circuit of relay 123 and closing an obvious circuit for relay 221' which operates. Relay 123 at its upper and lower alternate contacts disconnects the tip and ring contacts oi'plug 122 from the right windings of repeating coil 113 and connects these contacts over conductors 133 and 134 with the operators keyset circuit.

. Relay 221 upon operating closes an ob-. vious circuit to light lamp 222, connects ground over conductor 223 for supplying operating ground to the keys of keyset 224 and establishes a circuit from ground at its upper contact, through the winding and upper normal contacts of relay 225, conductor 133, upper alternate contacts of relay 123, tips of plug 122 and jack 314, lower back contact of relay 316, upper front contact of relay 315, lower back contact of relay 317 to battery through the winding of relay 318. Relay 318 operates in this circuit but relay- 225 being marginal does not receive sufiicient I current to operate at this time due to'the high resistance of relay 318.

Starting a link circuit to 7mm for the selected tmmlc Relay 318 upon operating establishes a startcircuit which may be common, for example to a group of ten trunks, extending from ground at the left contact of relay 318 over conductor 319 to battery through the winding of group relay 400 of the link circuit which has first choice access to'the group of trunks in which the selected trunk is located. Relay 400 upon energizing connects ground over its upper contact to segment 407 of the group commutator of the link finder 450, corresponding to the bank level in which the selected trunk appears, in the case assumed, the first or'lowermost segment, and establishes a circuit from ground at the back contact of relay 401, over the lower contact of relay 400, the lower'normal contacts of make: busy ack 402, conductor 403, the lowermost back contact of relay 500, to battery through the winding of relay-501. Relay 501 energizes in this circuit andestablishes a circuit for relay 502 extending from ground over the lower front contacts of relay 501, the inner lower back contact of relay 503, conductor 504, back contacts of vertical magnet 404 and rotary magnet 405, conductor 505 to battery through the upper winding of relay WVith relay 502 operated a circuit is now established for the vertical magnet404 of the trunk finder 450 which may be traced from battery through the winding of magnet 404, conductor 506, the lower back contact of relay 507, contact-of relay 502 to ground at the inner upper back contact of relay 500. Magnet 404 upon operating opensv at its back contact the circuit of relay 502 whereupon relay 502 in turn deenergizes, opening the circuit of magnet 404. Thus magnet 404 and relay 502 reciprocally control each other to cause the magnet 404 to step the brushes of finder 450 vertically step by step until the commutator brush 406 engages the grounded segment 407. When this occursa circuit is established for relay 507 extending from ground on segment 407, brush 406, conductor 408, the uppermost back contact of relay 500, the upper winding of relay 507, conductor i 508, the back contact of rotary magnet 405,

conductor 505 to battery through the. upper winding of relay 502. Relays 502 and 507 operate in this circuit, relay-507 looking over its lower winding and inner lower front contact, inner lower back contact of relay 500, conductor 509 to ground at the lower alternate contacts of vertical off-normal springs 409 which closed whenthe trunk finder 450 took the first step off-normal. Relay 507 at its lower back contacts also opens the operating circuit of the vertical magnet 404.

WVith both relays 502 and 507 energized a circuit is now established for the rotary mag net .405 extending from battery through the start'conductor 319 group relay400 releases oint of magnet 405. r relay 502 reciprocally control each other to winding of magnet 405, conductor 510,-the lowermostfront contact of relay 507, the con tact of relay 502, to ground at the innermost upper back contact of relay 500. Magnet405 upon energizing opens at its back contact the i previous traced circuit extend ng through the upper winding of relay 502 whereupon" relay 502 deenergizes in turn opening the cir-v Thus magnet 405 and cause magnet 405 to step the brushes of finder 450 over the terminals of the first bank level to which they were previously raised until the set of terminals is reached intlie level to which the selected trunk is connected. Tliereupon a circuit is established from battery through the winding of trunkrelay 321, the right contact of relay 318, the left normal contacts'of relay-322, inner lower contact of relay 315, conductor 323, bank terminal 410, brush 411, conductor 412, upper front contact of relay 501, winding'of relay 511 to ground through the lower'winding of relay 502; Re-

lays'321, 502 and 511 operate in this circuit,

relay 511 closing an obvious circuit for relay 503 and a locking circuit for relay 501 extending from battery through the Winding and inner lowerfront'contact of relay 501 the lower Contact of relay 511 to ground at;

the intermediate lower normal contacts of relay 512' for holding relay 501 operatedafter' relay 500 operates as later described; Relay 503 npon'operating closes at its innermost upper contact a shunt around the lower winding of relay 502, causing the release'of relay 502, closes'at its lower front contact an obvious operating circuit through the upper winding of relay 500 and at its lower inter inediatecontact prepares a circuit for relay 512'. Relay 500 uponoperating looks from oil-normal groundon conductor 509 over its innermost lower front contact and lower winding, conductor 513 to battery at the back contact of relay 413 andat itsuppermost back contact and innermost lower back con tact opens the initial operating and locking circuits of relay 507'. Relay '507 thereupon releases. I

At the trunk circuit upon theoperation of relay 321, a circuit is established for relay 3'17 extending from battery, winding of relay 317 inner front contact of relay 321 to n i elay 315. Relay 317locks directly to ground at the inner upper front contactof relay 315' over its inner upper front contact and opens the circuit of relay 318 which upon deenergizing disconnects ground fi-orn'start' condnctor 319 and 0 ens the o eratin circuit b of relay 321. Relay 321 is, however, held operated over conductor 323, innerlower" front contact of relay 315, left normal contacts of relay 322and the lower front contact of relay 321. When ground is removed'from round at the inner upper front contact of if there is-at the time no other trunk in the same 'group in a select-ive'condition.

an idles-antler Atthe time relay 501 opera-ted immediately following the starting of the-link circuit, a circuit was also established for relay. 514

extending from battery through tlie'winding of relay 514, over the lower back contact of 'test relay 515' to ground at the lower'fron't,

contact of relay 501. At its upper front contact relay 514 establishes a saturating circuit from battery through the lower winding of relay 515, front contact of relay 514, through I for the test relay 515 which may be traced the middle winding of relay 515 to ground at the lower front contactof relay 501. Re lay 515- does not, however, become energized sufiiciently 'toattract its armatures. At its lower contact, relay 514 establishes afcircuit for stepping relay-516 of the sender finder 550 which, extends from battery through the winding of relay 516, back contact of step ping magnet517, lower contact of relay 514 to'ground atthelupper backcontact of test relay 515. Relay 516 upon energizing conmeets the winding of the stepping magnet 517 to ground at the upper back contact of relay 515 whereupon magnet 517 energizesop'ening the'energizing circuit of, stepping relay 516.

Magnets 517 and 516 thus reciprocally control each other thereby advancing the brushes I of the sender finder 550'step by'step in search of an idle sender; As soon as a terminal set is reached to which'an idle sender is connected, a circuit becomes established for test operates quickly locking in a circuit "extending from ground over its upper front contact and upper Windingythenee as traced .to battery at the back contact of relay 601, opening at its upperjback contact the operating circuitsof relay 516 and magnet 517 and opening at its lower back contact the operating circuit ofrelay 514. o I

After an interval measured by its slow re leasing characteristic relay'514 deenergizes and if at this time the trunk finder has completed its operation and relay 503 has operated,a circuit is established forrelay 512 extending from battery through the winding of relay 512, the lower intermediate front contact of relay 503', the intermediate lower back contact :of relay 512, the upper back contact of relay 514, the lower front'contact of relay Cit 'front contact to ground at the upper front contact of relay 503, opens at its intermediate lower back contact its own 1n1t1al operatmg circuit, transfers the locking circuit of relay 501 from ground at the inter mediate normal contacts of relay 512 to ground through the upper back contact of relay 514,.the lower front contact of relay 515 and the lower front contact of relay 501, connects brushes 414' to 417, inclusive, of

'finder 450 to brushes 520 to 523, inclusive, of

sender finder 550, establishes a circuit extending in parallel through the windings of relays- 524 and 525 over the upper front contact of relay 512, brush 526, conductor 527, through the left and intermediate windings of relay 603, the upper normal contacts of relay 604, to ground at the inner upper contact of relay 605 and at its next-to-upper con tact connects batterythrough high resistance 583, the back contact of relay 524, conductor 534, brush 42 3, conductor 424, through the winding of relay 322 to battery forthe purpose of marking the trunk busy so long as the link circuit is engaged therewith. Relays 525 and 603 operate in the circuit traced but relay 524 being marginal, does not operate.

At its upper contacts relay 525 bridges the upper contacts of relay 501 in the holding circuits of relays 511 and 321 to hold the lat- "ter relaysoperated-following the release of relay 501 and at its lower contacts establishes an obvious circuit for relay 536 which closes an alternative holding circuit for relay 512 for holding relay 512 operated following the release of relay 503.'

Should a second trunk of the same group be selected at this timewith relay 500 operated and relay 507 deenergized and the group relay 400be operated, relay '400 will again mark the lowermost commutator terminal 407 as before but will now start the trunk finder normally having first choice access to the group of trunks in the first level of its bank and in the tenth level of finder 450. This start circuit extends from ground at the back contact of relay 401 over the lower contact of relay 400, lower normal contacts of jack 402, conductor 403, the lowermost front contact of relay 500, the innermost upper back contact of relay 507, conductor 528, the lower normal contacts of jack 418,thence through the relay of that link corresponding to relay 501. Since the commutator segments and bank multiples are slip multiplied in the well known manner, the trunk finder started will step vertically to its tenth bank level when it will be arrested by its commutator brush corresponding to'brush 406 engaging the tenth segment of its commutat or which is multipled to the segment 407. In a similar, manner should other trunks be placed in a calling condition in the same trunk group paddle wheel start circuit arrangement.

At the sender upon the operation of relay 603 an obvious circuit is closed for relay 606 which in turn closes an obvious circuitfor relay 600. Relay 600 disconnects battery through resistance 602 to make the sender busy to other sender finders,connects ground overits outer left front contact to the start lead 607 extending to the sender time alarm circuit and connects the right winding of the sender time alarm relay 700 to the lead 608 and over its inner right front contact prepares a circuit forrelay 609. Relay 606 also closes an operatingcircuit from ground at its inner lower front contact overconductor 610 to battery through the winding of relay 701 which operates closing ground to conductors 800, 801, 802, 900 and 901 for furnishing locking ground to the senderregister relays and closing a circuit over conductor 702 to battery through the winding ofrelay 611. Relay 611 operates to perform functions to be later described. also closes an operating circuit for transfei relays 803 and 804 in series over conductor 811, outer right back contact of relay 703, conductor 704, to ground at the inner upper front contact of relay 606. Relay 808 u'pon operating locks itself and relay 804 operated over its upper front contact, the upper back contact of relay 814, conductor 812, upper back contact of relay 612 to ground on conductor 704 and extends its locking ground over conductor 821, the right normal contacts and winding of relay 7 03 to battery. Relay 703 operates and locks over its right alternate contacts to ground onconductor-704 and opens the initial operating circuit of" relays 803'and 804. Relay 804 upon operat- Relay 606 s ing connects the operating windings of the relays 805 to 808, inclusive, of the first sender register to the contacts of thekey pulsing relays 705, 706, 715 and 716 in readiness to register the first digit keyed by the operator Registering the class indication- The trunks to which the sender has access are arranged in groups in accordance with the number of digits required to complete calls. Further subdivlsion 1n grouping may be made as follows: trunks requiring .autorequired to pulse out a single fixed number of digits or of trunks for which the senderis required to pulse outseveral different num-v bers of digits under the control of the opermay require a fixed number of digitsto be keyed or a. variable number of digits followed by an operationof'start key 226; automatic start of ringing or no ringing;

0.6 seconds timing between any two series ofimpulses sent out or 0.4 timing between any two series of impulses that do not require trunk huntin as the impulse series transmitted to set a connector switch. A class containing a variable number of digits may consist of digits requiring automatic start of ringing and also digits requiring no ringing. The polarity connected toleads 306, 308, 311 and 313 leading from each trunk circuit to the sender through the link circuit is determined by the arrangement of straps 301 to 304, inclusive.

With thesender now associated with the trunk circuit the following relays of the sender may or may not be operated, dependent upon the strapping in the trunkcircuit. If battery is connected to conductor 306, relay 613 operates in a circuit from conductor 306, brush'417, conductor-419, inner upper front contact of relay 512. brush 523, conductor 537, inner upper back contact of relay 614,

lower normal contacts and winding of relay f 613 to ground at the upper contact of relay 606. If battery is connected to conductor. 308,

relay 614 operates in a circuit from conductor 308, brush 416, conductor 420, next-to-innerupper contact of relay 512,.brush 522, conductor 529, upper back contact of relay 613, lower normal contactsand windingof relay 614 to ground at the neXt-to-upper contact of relay 606. :If battery is connected to conduct-or 311 andground to conductor 313, relay 618 operates in a circuit frombattery on conductor 311, brush 415, conductor 432, con tact 530 of relay 512, brush 521, conductor 531, lower back contact of relay 617, inner lower front contact of relay 611, lower back contact of relay 604, windings of polarized relays 618 and 619 in series, conductor 620, back contact of relay 711, conductor 712,upper back contact of relay 617, conductor 538, brush 520, contact 532 of relay 512, conductor 433, brush 414 to ground on conductor. 313, thus operating polarized relay 618, polarized relay'619 not receiving current in the proper direction to operate. Relay 618 in turn closes a circuit from battery, winding of relay 615,

lower -back contact of relay 616, contact of relay 618 to ground on conductor 704-. If battery is connected to conductor 313 and ground to conductor 311 current flows through the windings of polarized relays 618 and 619 in such a direction as to operate relay 619 which in turn closes a circuit from battery, winding of relay 616, lower back contact of relay 615, contacts of relay 619, to ground on conductor 704. Either relay 613 or relay 614 upon operating looks from ground at contacts of relay 606 through its own winding and lower alternate contacts to'battery through resistance 621. Either relay 615 or relay 616 upon operating locks frombatt-ery through its winding and upper front contact to ground on conductor 704.

Relay 613 if operated connects conductor 306 over the path just traced to conductor 537, thence over the inner upper back contact I of relay 614, lower front contact of relay 613,

upper back contact of relay 612, conductor 623, windings of relays 715, 716 and 7 24 to 24 volt battery, and connects conductor 308 over the path just traced to conductor 529 thence over the inner upper front contact of relay 613, lower back contact of relay 612, conduc tor 622, windings of relays 705, 706 and 714 to 24-volt battery; Relay 614, if operated, connects conductor 306 over the path traced to conduct-or 537, thence over the inner upper front contact of relay 614, lower back contact of relay 612, conductor windings of relays 705, 7 06 and 714 to 24-volt battery, and connectsconductor .308 over the path traced to conductor 529 thence over the upper back contact of relay 613, lower front contact of relay 614, upper back contactof relay 612, conductor 623, windings ofrelays 715, 716 and r 24 to 24-volt battery. Circuits for class relays 707 to 710, inclusive, are closed as follows lVith relays 614 and 616 operated, class relay 707 is operated in a circuit from battery through its winding. conductor 713, inner upper front contact of relay 616 to ground at the upper front contact of relay 614; with relays 613 and 616 operated class relay 708 is operated in a circuit'from battery through its winding, conductor 717, intermediateupper contact of relay 616, upper front contact ofrelay 613 to ground at the upper back contact of relay 614; with relays 614 and 615 operated class relay 709 is operated in a circuit from battery, through its winding, conductor 718, inner upperfront contact of relay 615, to ground at the upper front contact of relay 614; and with relays 613 and 615 operated, class relay 710 is operated in a circuit frombatte'ry through its winding, conductor 719, intermediate upper contact of relay 615, upper contact of relay 613 to ground at the upper backcontact of relay 614.

The following table indicates the different.

sender relays that are operated by the transposition of leads 306, 308, 311 and 313 in the associated trunk circuit to give the four-class In the case assumed, the trunk of Fig. 3 is a trunk of a fixed foundigit class requiring the automatic start of ringing from the sender only in case the call is being completed by an inward toll operator and requiring a short interval of 0.4 seconds between the last two impulse series which are to be transmitted 1 therefrom to set the connector switch and,

consequently the straps 301 to 304 are connected as shown to connect lead 306 to lead 305 and thence over the lower back contact of relay 316, tips of jacks 314 and plug 122, upper alternate contacts of relay 123, conductor 133, upper normal contacts and winding of relay 225 to ground at the upper contact of relay 221; lead 308 to lead 307 thence over the upper back contact of relay 316, rings of jack 314 and plug 122, lower alternate contacts of relay 123, conductor 134, upper back contact of relay 227 to battery through resistance 228; lead 311 to lead 309 thence to ground through one winding of the control relay not shown of the first selector 300 in which the trunk terminates; and lead 313 to lead 312, thence to battery through the other winding of the control relay of the'first selector 300. Thus as indicated in the preceding table, relays 614, 616 and class relay 707 are operated. As previously described relay 614 upon operating connects 24.-volt battery through the windings of relays 705, 706 and 714 to conductor 306 and thence as traced to ground through the winding of relay 225 at the operators keyset circuit, thereby operating relay 225 which locks over its upper alternate contact through resistance 228 to battery, closes the circuit of relay 227 over its lower contact, the upper back contact of relay 229 to ground at the upper contact of relay 221 and closes the circuit of lamp 230 from battery through the lamp, the lower back contact of relay 229, the lower contact of relay 225, upper back contact of relay 229 to ground at the upper contact of'relay 221. The lighting of lamp 230 at this time is a signal to the operator that the sender is in condition to receive and register the first digit.

Relay 227 upon operating connects 48- volt battery through resistance 231 and its lower front contact to conductor 232 for supplying battery to key contacts of keyset 224 and connects the keyset conductors 233 and 234 over its upper alternate and inner lower front'contacts to conductors 134 and 133 and thence over the circuits traced to 24-volt battery through the windings of pulsing relays 715, 716 and 724 and the windings of pulsing relays 705, 706 and 714, respectively.

Keying the caZZecZ'Zi/ae designation It will be assumed" that the operator in order to establish a connection to the line 360,

the designation of which is the four-digit number 1379, depresses the keys 235, 236, 237

and 238 in the order named. Upon the de-' pression of key 235 to register the thousands digit 1 ground on conductor 223 is con.-

nected through low resistance 239, the contacts of key 235, conductor 234, thence as traced to 24-volt battery, through the windings of impulse relays 705, 706, and 714. Due

to the inclusion of low resistance n30,suflicient current flows to operate both the sensitive relay 714 and the marglnal relay '7 06, but polarized relay 705 does not receive current in the proper direction through its winding to cause its operation.

Relay 714 upon operating, with transfer relay 803 operated as previously described, establishes a circuit extending from ground at its contact over conductor 822, inner lower front contact of relay 803, to battery through the winding of transfer relay 813. Relay its contact over conductor 720, inner low contact of transfer relay 804, to battery through the lower winding of register relay 805. Relay 805 operates and locks over its upper winding and inner lower front contact to ground on conductor 800.

When the operator releases the depressed key 235, relays 706 and 714 release, relay 714 removing the shunt from around the winding of transfer relay 814, whereupon relay 814 operates in the locking circuit of relay 813, opening at its upper back contact the locking circuit of transfer relays 803 and .804 whereupon these relays release. Relay 804 disconnects the operating circuits extending from the windings of relays 805 to 808 inclusive of the first register from the contacts of impulse relays 705, 706, 715, and 16, and relay 814 upon operating connects the con tacts of the impulse relays to the windings of relays 815 register.

1Vhen the operator depresses key 236 to register-the hundreds digit 3, 48volt battery on conductor 232 through low resistance 231 is connected over the contacts of key 236, conto 818, inclusive, of the second f I windingof transfer relay S23.

,tor 812,.but relay 824 being -as relay 714 remains operat 'ductor 234, thence as traced to 24-volt battery through the windings of impulse-relays 705, 706 and 714. The direction of current now flowing throughthe-windings of these relays is such as to operate the pola i7ed relay 705 and since a low resistance has been included in the circuit relays 706 and 714 also operate. Relay 714up'on op'erating with transfer re.- lay 814 operated closes a circuit from ground over conductor 822, inner lower haclr of transfer relay .803, lower front contact of transfer relay 813, to batterythrough the 1 nlu )0 may on operatesfland locks in series with the winding of relay 824, middle upperfront contact of relay 823, conductor 8 3'l, upper. hack contact of transfer relay 904 to ground .duc-

W does not operate at this time. Relay 706 upon operat. lg

closes circuit extending fromground at its contact over conductor 720, inner lower front contact of transfer relay 814. to battery through the lower windin g of register relay 815. Bela 815 u ion oueratln locks over its upper winding and inner'lower front con-- tact to ground on conductor 801. clay 705 upon operating closes circuit extending from ground. at its contact over conductor 721, lower contact'of transfer relay 814 to battery thrr-iugh the upper Windin of register relay 816. Relay 81-6 upon ope looks over its'lower winding and front con act to ground on conductor 801.

' VVhen the operator releases depressed key 236, relays705, 706 and 714' release, relay714 opening the shunt around the winding of transfer relay824,-whereupon relay 824 operates in the locking circuit of relay 823, opening, at its back contact the locking circuit oftransfer relays 813 and 814 whereupon these relays release. Relay disconnects the operating circuits of regis relays 815 to 818 inclusive, from the contacts of impulse relays 705, 706, 715 and 716 and relay of theserelays is such as to operate polarized relay 705 and since high resistance 240 has been included in the operating circuit marginal relay 706 does not operate but sensitive relay '7 14 operates. Relay? 14 upon operating -w'th transfer relay 813 now released and transfer relay 823 operated, closes a-circuit from ground at its contact over conduct-or i operateiat this time. IDgClOSQS a circuit extendlng from ground at 822, inner lower back contacts of relays 803 and 813, inner lowerfront contact of relay 823,. conductor. 832, winding of transfer relay -903 to battery. Relay 903 operates and locks in series with the winding of transfer relay" 904, middleupperfront contact of relay 903,

back contact of transfer relay 9l4 to ground on conductor 812, but relay 904 being shunted as long as relay 714 remains operated does not Relay 705 upon operatits jc'ontact over conductor 721, lower contact of transfer relay 824' to battery through the upper windingof register relay 826. .Relay .826 operates and locks over its lower wind-' ing and lowercontact to ground on conductor802.r.q J

5 l Key 237 also closes a circuit from ground on conductor-223 through low resistance'241,

' right contacts of key 237, conductor233 and thence as traced to 243-y0lt batterythrough the windings of impulse relays 715., 716 and p The current now flowing is not in the ,pr,oper-direction to operate polarized relay Q715but since only low resistance 241 has been included in the operating circuit both relay 724 and marginal relay 716 operate. Relay 724. upon operating merely duplicates the function ofrelay 714, already described and relay 716 connects gr'ound'at its contact over conductor 722, upper front contact of transfer relay 824 to battery throughthe upper winding ofregister relay 828. I Relay 828 operates and locks over its lower winding and lower contact to ground on conductor 802.

, vVhen the operator releases depressed key 237 impulse relays 705, 714, 716 and 724 release,"relays 714 and 7 24 opening the shunt around the winding of transfer relay 904 whichnow operates in the locking circuit of relay 903 opening, at its back. contact the locking circuit of transfer relays 823 and 824 whereupon these latter relays release. Ree lay 824 disconnects. the operating circuits of the register. relays] 825 to 828, inclusive,

lay 904 upon operating connects thejcontacts I of the impulse relays .to the windings of regis-. ter relays 905 to" 908, inclusive.

In responseto the depression of key:238 for the units digit 9 48 voltbattery is connected through low resistance 231 over conductor 232, the right contacts of key'238, conductor 233 andthence as traced through the windings of impulse relays 715,716 and 724 .to

. 24-volt battery. Due to the connection of 48- Volt' battery through a low resistance all these impulse relaysrespond. Relay 724 :upon operating connects ground at its contact, over conductor 822, inner lower back contacts of transfer relays 803, 813, 823, conductor 833, inner lower front contact of transfer relay 903, conductor 911, inner left front-contact of class relay-707 which was assumed to be-operated, conductor 624 to batfrom the contacts of the impulse relays. Re-

and locks overrits lower winding and lower contact to ground on conductor 900. Relay 7115 upon operating closes circuit extending from ground at its contact over conductor 723, inner upper front contact of relay 904 to battery through the upper winding of rea lay 907 and in parallel through the winding of relay729 to battery. Relay 907 operates and locks'over its lower winding and lower contact to ground on conductor 900. Relay 729; also operates but is ineffective at this time.

Key 238 also closes a circuit from ground through low resistance 239, high resistance 242, left contacts of key 238, conductor 234, thence as traced to 24-volt battery through the windings of impulse relays 705, 706 and 714 but dueto the direction and strength of the current flowing only relay 714 operates duplicating the function of impulse relay 724 already described.

- VJ hen the operator releases the depressed key 238, impulse relays 714, 715, 716 and 724 release, relays 7 14 and 724 opening the shunt around the winding of relay 612, whereupon relay 612 operates in the locking circuit of relay 625, disconnecting ground from conductor 812 at its inner upper back contact thereby releasing transfer relays 903 and 904.

Transfer relay 904 upon releasing disconnects V the'o eratin circuits of register rela s 905 and 908, inclusive, from contacts of the iinpulse relays. Relay 612 upon operating disconnects the windings of impulse relays 705, 706 and 714 at its lower back contact from the impulse path previously traced to conductor 233 at the keyset-circuit and extends the impulse path over its lower front contact, conductor 626, right back contact of relay 725, inner left back contact of relay 726 to 48-Volt battery through the right winding of relay 727, and disconnects the windings of impulse relays 715, 716 and 7 24 at its upper back contact from the impulse path previously traced to conductor 234 at the lreyset circuit and extends this impulse path over its upper front contact, conductor 627, inner left back contact of-relay 725, outerleftback contact of relay 726 to 48-yolt battery through the leftwinding of relay 728.-

At the keyset conductor extends through the winding of polarized relay 243 to 24-volt battery and: conductor 234 extends through the winding of polarized relay 244 to 24-yolt battery. Relays 243 and 244 both operate but relays 727 and 728 being marginally wound do not operate at this time. With relays 243 and 244 both operated an obvious circuit is closed for relay 245 which' looks to ground at the upper contact of relay 221 and connects ground over its upper'confacts to conductor 234 whereby marginal relay 727 in the sender operates and lo'cksin a circuit extending from battery through the winding'of relay 7 26, left Winding and contact of'relay 727, to ground on conductor 704. Relay 7 26 upon operating disconnects the.'opcrating windings of relays 7 27 and 7 28 from windings of polarized relays 243 and 244at the keyset circuit, relay 243 now releasing but relay 244 being held operated over the upper contacts of relay 245. Relay 243- upon releasing closes a circuit from ground atits back contact, lower contact of relay 245, winding of relay 219 to battery. Relay 219 operates and opens the circuit of relay 218 which upon releasing in turn releases relay the circuits previously traced through the 221. Relay 221 upon releasing in turn releases relays 245, 244, 219, 225 and 227 and extinguishes lamps 222 and 230. Relay 221 upon releasing also. releases relay 123 in the cord circuit. The operators keyset circuit is now in normal condition.

If the operator disregards the pilot lamp 230 and starts keying a designationbefore the sender is attached and relay 227 has been operated from the sender,.a circuit will be closed for relay 229 from batterythrough its winding, inner lower baclr contact of relay 227, conductor 234 to ground on conductor 223 through contacts of any operated key of the keyset 224. Relay 229 upon operating locks over the left contact of key 216, upper? front contacts of relay 229 to ground at the upper contact of relay 221 and at its lower front contact connects lamp 230 in a flashing circuit with interrupter 246. To prepare the keyset for use the operator must press key? 216 to release relay 229. Transmission of impulses to selcctor switohes Returning to a consideration of the'sender it will be recalled that relay 611 operated when the sender was seized. Upon its. operatlon a circuit was established for operating impulse generating relays 730 and 7 31'ex- 1 tendingfrom ground at its inner upper front contact, conductors 628, 629 and 630, resistances 732 and 733, resistance'735 to battery andin parallel over the lower contactsof jack 734, left windings of polarized relays 730 and 731, upper contacts of jack7 34, re

sistance 736 to battery in preparation for" impulsing, relays 7 30 and 731 both operating. At this time, the impulsing loop to the'first selector previously traced through the windings of relays 618 and 619 isnow closed at the sender through the contacts of relay 7 30 and back contacts ofrelay 711 in parallel until relay'7l1 operates at the end of the synchronizing impulse as will be described. 'Relay 611 also at its lower front contact switches the condenser 631 and resistance 632 across the impulsing conductors 531 and 538 extending from the sender to' the first selector 300; At

this time condenser 742 associated with the impulse generating relays 730 and 731' is also charged in a circuit extending from ground through condenser 742, upper-1 normal contacts of jack 741, right windings of relays 7 30 and 731, lower normal contacts of jack 741 to battery through resistance 736.

It will be assumed that the sender is arrangedgto start the transmission of the first series of impulses as soon as the firstdigit has been registered on calls of classes A and C having afixed-number of digits and to delay the transmission of the first series of impulses until after the first two digits have beenregisteredon calls of classes B and Dhaying a variable number of digits. 'For this purpose, straps 651, to 663, inclusive, of Fig. 6 straps 862 to 865 of Fig. 8 and straps 955 and 956 of Fig. 9 are connected asshown. As soon as the first digit has been registered on the .shunted does not. operate, at this time; lay 809 upon operating closes a circuit from ground on conductor'630, inner lower front contact: of relay 80,9, conductor 635, upper.

relays of groups 805 to 808, inclusive, and transfer relay 803has released as previously described, a circuit for transfer relay 809 is established extending from battery through the winding'of relay 809, upper back contact of transfer relaySlO, lower back contact I of relay803, straps 651 and 652, conductor 681,"outer ri 'ht back contact of relay 737, relay 737 not being energized since the class assumed is thefiXed four-digit class, conductor 738, straps 653 and 654, conductor 835,

inner left front contact of relay 703, conductor.740, left back contact of relay 836, conductor 633, to ground at the inner lower front contact of relay 616.,

-Relay 809 upon operating locksthrough the upper winding ofrelay 810, lower front contact of relay'809, conductor. 852, rightback contact of counting relay 842, conductor 634 to ground at the middle lower "front contact of relay 606, but'relay 810 being back contact of relay 636, back contact of relay 637, "upper back contact of relay 638,

inner lower back contact of relay 604, conductor 639, front contact of relay 731, upper contacts of jack 734, left windings of relays 731 and 730, lower contacts of jack 734, to

battery. through resistance 735 and in parallel with the left windingsof. relays 731 and 730 to battery through resistance 7 36., The

a} current flowing through the left windings of relays 730 and 731 now decreases since the left, windings of these relays are now con .nected in a. c1rcu1t from ground'on conductoi Re,- I

630, through. resistances 732 and 733 to is reached when the relays 730" and 731 both release differentially.

. w When relay 7 31 opens its front contact the charging path for condenser 742 through the right windings of relays 730 and 731 prev1-= ouslytraced is again effective, current now flowing througlr the right windings .in thej reverse direction and these relays continuing to release andto remain normal until con denser 742 approaches full charge condition and the current in the initial energizing circuit through the leftiwindingsof these re--s;

lays has reached operating strength, when F I relays t30and (31w1llaga1n operate. TllZS pulsing action continues until ground is removed from the armature of relay 731by the releaseof transfer relay809,-following the to transmission of impulses for the first digit, by the release of transfer relay 819, followingthe transmission'of impulses for the second digit, by the'release' of transfer relay 829 following the transmission of impulses for the third digit, the release of transfer relay 909 following theitransmission of im-, pulses for the fourth orlast digit and the timing for trunk. hunting between" the trans M mission of'digits has been allowed.

Upon-the first-release of relay 731- a circuit is established from ground on conductor 639, back contact of relay 731, conductor 743, right back contact of counting relay 836, right back, contact of counting relay 838, back contact of counting relay 854, to battery through the winding of counting relay 853. Relay 853 upon operating locks throughthe winding 1 of relay 854, front contact of relay 853, left back contact of relay-838 to ground on con- 7 ductor'634, but relay 854 being shunted does .not operate until relay 7 31: again operates. Relay 854 upon operating extends ground from conductor 634, over the 'left back coir,

v tact of relay 838, inner left contact of relay @854, to the armatures of the Nos. 6 and 7 counting relays 849 and 851 for affording locking ground for these relays, over the back contact of relay 851 tothe armatures of the Nos. 3 to 5 counting relays 843, S45 and 847 for locking these relays when operated, and at its outer left contact connects ground from conductor 634, over conductor 640 to battery, through the winding of p'ulse-help relay 711. Relay 711 upon operating closes a, shunt around the windings of relays 618 and 619, extending from conductor 620, right front contact of relay 711 to conductor 641 thusremoving these relays from the impulseitmg circuit extending from the sender to the 

